It is common practice to form high strength aircraft structural components by forging the article from an aluminum alloy and then subjecting the forging to a machining operation to bring it to finish size. A typical element formed in this manner might have transverse flanges of fairly heavy cross-section joined by webs of substantially smaller cross-section. When such articles are forged by conventional forging processes it is very likely that the finished forging will contain internal stresses due to cooling from the solution treating temperature. When machining takes place, these stresses produce such phenomena as "oil canning" in the web joining the flanges and overall warpage of the article. This is an intolerable situation because it renders the article unusable and yet may not make its appearance until the last stages of an expensive series of operations on an expensive article. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a forming and heat treating process for aluminum alloy which relieves internal stresses.
Another object of this invention is the provision of a process for forming and heat treating an aluminum alloy article which, when machined, will not suffer from distortion and warping or the like, which would render the article unusable.
A further object of the present invention is the provision of a process for forming and heat treating an aluminum alloy in which a stress relieving restriking operation can take place before aging occurs in the forging.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of steps set forth in the specification and covered by the claims appended hereto.